1. Field of the Invention
The present invention relates to a sheet processing apparatus and an image forming system.
2. Description of Related Art
In an electrophotographic image forming apparatus, when an image forming process includes a step of heating paper sheets, such as a fixing step, water evaporates from the heated sheets and causes an uneven distribution on the moisture content on the sheet, which may cause curling of the sheet such as waving.
A sheet processing apparatus is known that humidifies a sheet with an image formed thereon and passes the sheet through waving uneven parts to correct the curling of the sheet (For example, Japanese Patent Laid-Open Publication No. 2010-1089).
FIG. 9 illustrates an example of such a sheet processing apparatus 500 in this structure.
The sheet processing apparatus 500 includes, for example, a receiver 510 receiving a sheet from an image forming apparatus (not shown), a humidifier 520 humidifying the sheet, a decurler 530 having uneven parts 10, 20, 30 applying a pressing force to the sheet being conveyed, an ejector 540 discharging the sheet to the exterior of the apparatus, a first conveyor 550 conveying the sheet from the humidifier 520 to the decurler 530, and a second conveyor 560 conveying the sheet from the decurler 530 to the ejector 540.
However, such a sheet processing apparatus has a conveying path having a certain length between the humidifier 520 and the decurler 530. Some of a proper amount of water added to the sheet at the humidifier 520 evaporates from the sheet passing through the conveying path. As a result, the moisture content of the sheet may become improper at the decurler 530, which may preclude a desired decurling performance.